Validation and reproducibility of a short food frequency questionnaire for cardiovascular prevention.

Background: Diet strongly influences cardiovascular risk. Dietary evaluation is a major issue in cardiovascular prevention, but few simple tools are available. Our team previously validated a short food frequency questionnaire; a new version of this questionnaire (Cardiovascular Dietary Questionnaire 2 [CDQ-2]) is easier to complete and more reliable.

Aims: To validate CDQ-2 in comparison with the original version, and to test its reproducibility.

Methods: CDQ-2 has 17 closed-ended questions; it provides a global dietary score that is a combination of specific scores for saturated, monounsaturated and omega-3 fatty acids, and fruit and vegetables. CDQ-2 was validated against the original version in two groups, who completed both questionnaires: 99 patients with cardiovascular risk factors and 50 healthy subjects. Reproducibility was assessed with 27 health professionals who completed the questionnaire twice, with a 1-month interval.

Results: The correlation coefficients of the scores between the two questionnaires ranged from 0.65 (monounsaturated fatty acids) to 0.93 (fruit and vegetables) (all P<0.001). The percentage of subjects classified in the same quartile by both questionnaires ranged from 56% (omega-3 fatty acids) to 78% (fruit and vegetables). The percentage of subjects classified in the same or adjacent quartile ranged from 91% to 99%. The intraclass correlation coefficients, which assessed reproducibility, ranged from 0.61 (fruit and vegetables) to 0.88 (saturated fatty acids) (P<0.001).

Conclusions: This new version of the short dietary questionnaire shows good reproducibility and correlations with the original version; use and reliability are improved, which makes CDQ-2 a valuable tool for cardiovascular prevention.